1. Field
The presently claimed invention relates generally to communication systems, and more specifically to associating multicast groups to facilitate the interoperability of multiple client-devices based on host and client capabilities.
2. Background
The Wireless Mobile Digital Display Interface (WMDDI) is an extension of the MDDI Standard to wireless networks, as disclosed in U.S. Pat. No. 6,760,772 and related patent applications. The WMDDI protocol supports a secure data exchange between one host-device, such as a mobile device such as a cell-phone or a personal digital assistant (PDA), and a wide range of simultaneously accessible client-devices, such as wireless displays with embedded capabilities (such as audio/video decoding and reproduction, or HID capabilities). Direct communication between client-devices is not supported; only client to host and host to client asymmetric communications are supported. The communication is asymmetric in the sense that a much larger amount of data is expected to be exchanged in the forward link, that is, from the host to the client.
A WMDDI system consists of a single host-device and one or more client-devices with whom the host-device is able to establish an association and secure communication.
The number of clients is constrained by interoperability of the devices in the system. This interoperability depends on several factors such as:
bandwidth/delay requirements of the multimedia application;
requirements and capabilities of the client-devices because clients may have different processing capabilities, storage capabilities, display resolution and refresh rate capabilities, quality of service (QoS) requirements, etc.;
channel conditions, because interference may cause degradations, simultaneous access-requests from multiple devices may cause delays, etc.;
lower-layer capabilities; and
other related factors.
An example of an application that benefits from the creation of several multicast groups is scalable video coding. In scalable coding, every layer would be mapped to a multicast address. For example, a meeting where a video presentation has to be sent to personal display devices (personal computers or cell phones) each with different display resolutions. If the host device is running an application able to provide scalable video coding and the client devices also support scalable video coding, it is possible to efficiently broadcast the video content instead of sending the content unicast. To do so, clients with similar scalability properties, such as same resolution, will be part of a particular multicast group. There may be as many multicast groups as different resolution displays; for example, one multicast group could target quarter common intermediate format (QCIF) resolution and another video graphic array (VGA) resolution. All QCIF devices would be part of the QCIF-multicast-group and all VGA devices would be part of the VGA-multicast-group and the QCIF-multicast-group. The host would broadcast the base layer of the compressed video stream to the QCIF-multicast-address (both QCIF and VGA devices would be able to receive it), and the enhancement layer of the compressed video to the VGA-multicast-address (only VGA devices would be able to receive it). Another use of scalability may be to adapt video broadcast to several QoS based on SNR scalability.
There is, therefore, a need in the art for an association procedure that allows establishing/joining several multicast groups to facilitate the interoperability of multiple client-devices based on host and client capabilities.